In most machines of the mentioned type, the tool is arranged above the workpiece. The tool is also pivotal about a vertical axis to adjust a crossed-axes angle. To transmit the rotary movement from the drive motor to the tool, gear drives are used, which, aside from spur gears, also include pairs of bevel gears. Bevel gears having a quality which is required for precision working machines are expensive to manufacture and their clearance-free installation is very time consuming and, therefore, expensive. The workpiece is clamped in the mentioned machines on a table which is elevationally adjustable in vertical guideways and carries out with said table a movement in the sense of a center distance reduction between the geometric centers of the workpiece and the tool. This movability of the workpiece brings about sometimes difficulties in the case of machines having automatic workpiece-feed devices, in particular when the machines are changed over to different workpieces.
Also a machine has become known, in which the workpiece is arranged stationarily above the tool and all movements which are required for machine adjustment and working are carried out by the tool (German AS No. 1 121 907). A disadvantage of this design is that all guideways facilitating a machine adjustment and--even more--for working lie in the chip area and are thus exposed to the risk of the quick wear.
Therefore, the basic purpose of the invention is to provide a machine, which is suited for an automatic workpiece feed, in which the guideways are arranged mostly outside of the chip area and which has a simple drive arrangement for the tool.
The purpose is inventively attained with a machine having the tool arranged above the workpiece, the workpiece stationarily oriented below the tool, all guideways for guiding the movement of the tool being oriented above the workpiece and the drive for the tool being accomplished without the use of bevel gears. With this design of machine, it is possible to work the most different of workpieces. The stationary mounting on a rigid machine base permits also (1) the working of wave-shaped or undulating surfaces on the workpieces, (2) the tool which carries out all movements to be positioned above the workpiece and thus results in all guideways to be positioned outside of the chip area, and, finally, (3) the free passage of the workpiece under the tool permits a problemless automatic workpiece feed and discharge.
A problemless drive of the tool which is mounted in the movable and position-changeable tool head by a stationarily arranged drive motor occurs in a very advantageous manner through a Cardan shaft. In order to keep the rotary guide for the tool head clearance-free or to a closely specified tolerance and to thus avoid manufacture inexactnesses caused by the combined weight of the tool head, the tool and the drive shaft, the rotary clamping mechanism is initially tensioned in the vertical direction.
While one embodiment of the machine is suited only for precision working methods utilizing a purely radial feed of the tool, thus for example for the plunge shaving, gear rolling and similar methods, the machine is also suitable for other shaving methods, for example the parallel, diagonal or underpass shaving. It is thereby advantageous, if the adjusting carriage is composed of multiple parts, each relatively movable to the other. Gears according to all conventional methods can be shaved on a so-designed machine. If crowned teeth are to be produced, then a guide rule used in association with the adjusting carriage is possible, which guide rule results in a control of the movement of the tool head. This device which is very simple in its design can be enlarged upon in its range of use when wide gears are to be provided with a crowned surface or when teeth having crowning on only one side or other surface characteristics, for example a conical characteristic, are to be produced.